Cars and Light-Duty Trucks—Tier 3

Introduction

Tier 3 emission standards for light-duty vehicles were proposed in March 2013 [2839] and signed into law on March 3, 2014 [2999]. The Tier 3 standards—closely aligned with California LEV III standards—are phased-in over the period from 2017 through 2025. The regulation also tightens sulfur limits for gasoline.

The structure of Tier 3 standards is similar to the Tier 2 standards—manufacturers must certify vehicles to one of seven available “certification bins” and must meet a fleet-average emission standards for their vehicle fleet in a given model year. The standards are more stringent than Tier 2 standards and include a number of other important changes:

Both the certification limits (bins) and the fleet average standards are expressed using the sum of NMOG+NOx emissions,

The bins are named using their corresponding NMOG+NOx limit in mg/mi. The highest emission bin—Bin 160 (NMOG+NOx = 160 mg/mi)—is equivalent to Tier 2 Bin 5,

Information and regulatory announcements on Tier 3 regulation can be found in the EPA Tier 3 web page [2838].

Tier 3 FTP Standards

Certification Bins

Manufacturers must certify their vehicles to one of the seven emission bins shown in Table 1. Vehicles are tested over the FTP-75 test procedure (the NMOG+NOx limits must be additionally met over the HFET cycle). The standards are applicable to all vehicles, regardless of the fuel type.

Table 1Tier 3 Certification bin standards (FTP; 150,000 miles)

Bin

NMOG+NOx

PM*

CO

HCHO

mg/mi

mg/mi

g/mi

mg/mi

Bin 160

160

3

4.2

4

Bin 125

125

3

2.1

4

Bin 70

70

3

1.7

4

Bin 50

50

3

1.7

4

Bin 30

30

3

1.0

4

Bin 20

20

3

1.0

4

Bin 0

0

0

0

0

* In MYs 2017-20, the PM standard applies only to that segment of a manufacturer’s vehicles covered by the percent of sales phase-in for that model year, Table 3.

Bin 160 NMOG+NOx limit is equivalent to the sum of NMOG and NOx limits in the Tier 2 Bin 5. Bin 30 emissions are equivalent to Tier 2 Bin 2.

The EPA bins and the California LEV III emission categories have the same emission limits, to harmonize the federal certification testing with California requirements.

Fleet Average NMOG+NOx Standards

Tier 3 standards include a fleet average NMOG+NOx limit that must be met by each manufacturer. The fleet average NMOG+NOx limit is phased-in starting from 2017, and reaches 30 mg/mi in 2025 (Table 2). This final Tier 3 fleet average limit is applicable to all vehicle categories—an important change from the Tier 2 regulation that allowed more relaxed fleet average emissions from heavier vehicle categories.

Table 2Tier 3 fleet average NMOG+NOx FTP standards (mg/mi)

Vehicle Category

2017*

2018

2019

2020

2021

2022

2023

2024

2025

LDV, LDT1

86

79

72

65

58

51

44

37

30

LDT2, LDT3, LDT4, MDPV

101

92

83

74

65

56

47

38

30

* For LDVs and LDTs over 6,000 lbs GVWR and MDPVs, the fleet average standards apply beginning in MY 2018.

PM Standards

Tier 3 PM standards apply to each certified vehicle separately, they are not fleet average standards. However, due to uncertainties in regards to future vehicle technologies—such as gasoline direct injected engines or start-stop systems—and PM measurement methods at ultra-low emission levels, EPA adopted a five year phase-in period for PM standards. The phase-in schedule is based on percentage of sales, Table 3. A relaxed in-use FTP PM standard of 6 mg/mi applies during the phase-in period.

Table 3Phase-in of Tier 3 PM FTP standards (mg/mi)

Phase-In

2017

2018

2019

2020

2021

2022

Percentage of sales

20%*

20%

40%

70%

100%

100%

Certification standard

3

3

3

3

3

3

In-use standard

6

6

6

6

6

3

* Manufacturers comply in MY 2017 with 20% of their LDV and LDT fleet under 6,000 lbs GVWR, or alternatively with 10% of their total LDV, LDT, and MDPV fleet

Supplemental Exhaust Emission Standards

SFTP Testing. In addition to FTP testing, vehicle emissions are measured over the supplemental FTP (SFTP) cycles, including the US06 and SC03. The composite SFTP emission result is calculated using the same formula that was used in Tier 2 regulation:

SFTP = 0.35 × FTP + 0.28 × US06 + 0.37 × SC03

NMOG+NOx Standards. Manufacturers voluntarily determine the specific SFTP NMOG+NOx standards for the certification of each vehicle family. (These self-selected standards are analogous to family emission limits, FEL, used in heavy-duty highway engine standards.) Such self-elected standards must not exceed 180 mg/mile. The fleet average SFTP decreases from 103 mg/mi in 2017 to the final 50 mg/mi in 2025 (Table 4).

Table 4Tier 3 fleet average NMOG+NOx SFTP standards

Emission

2017*

2018

2019

2020

2021

2022

2023

2024

2025

NMOG+NOx (mg/mi)

103

97

90

83

77

70

63

57

50

CO (g/mi)

4.2

* For LDVs and LDTs over 6,000 lbs GVWR and MDPVs, the fleet average standards apply beginning in MY 2018.

US06 PM Standards. The SFTP standards for PM are to be met over the US06 test, representing aggressive highway driving. Similar to the FTP standards, the US06 PM standards are phased-in over a five year period based on the percentage of sales, Table 5. The PM standards are applicable to each vehicle family (i.e., not fleet average). In-use standards are more relaxed than the certification standards.

Table 5Phase-in of Tier 3 PM US06 standards (mg/mi)

Phase-In

2017

2018

2019

2020

2021

2022

2023

2024

Percentage of sales

20%*

20%

40%

70%

100%

100%

100%

100%

Certification standard

10

10

6

6

6

6

6

6

In-use standard

10

10

10

10

10

10

10

6

* Manufacturers comply in MY 2017 with 20% of their LDV and LDT fleet under 6,000 lbs GVWR, or alternatively with 10% of their total LDV, LDT, and MDPV fleet

Vehicles that do not meet the final Tier 3 PM standards (a declining percentage of sales through MY 2021) are referred to as interim Tier 3 vehicles.

Useful Life

Tier 3 standards apply over a useful life of 150,000 miles or 15 years, whichever occurs first. This requirement is identical to the California LEV III program approach.

However, the Clean Air Act precludes EPA from requiring a useful life longer than 120,000 miles for lighter vehicles, including LDVs and LDT1s. Therefore, manufacturers are allowed to certify their LDV and LDT1 vehicles to a useful life of 120,000 miles (and 10 or 11 years, depending on vehicle category and weight).

If any vehicle families are certified to the shorter useful life period, a proportionally lower numerical fleet-average NMOG+NOx FTP standard applies, calculated by multiplying the respective 150,000 mile standard, Table 2, by 0.85 and rounding to the nearest mg/mi. Standards for other pollutants and other test cycles (such as SFTP) remain the same regardless of the chosen useful life period.

Tier 3 Fuel Standards

The Tier 3 fuel standards require that federal gasoline contains no more than 10 ppm of sulfur (down from 30 ppm) on an annual average basis by January 1, 2017. Eligible small volume refiners must comply by January 1, 2020. The regulation maintains the prior per gallon caps—80 ppm at the refinery gate and 95 ppm downstream.

An important purpose of the updated sulfur standard is to reduce the negative effect of sulfur on three-way catalyst performance; facilitating the achievement of the 150,000 mile full useful life emission limits. The 95 ppm downstream sulfur cap will still be a challenge for some sulfur-sensitive catalyst technologies, such as NOx adsorbers, that are used on direct injection, lean burn gasoline engines. Many lean burn catalyst technologies require a sulfur cap on the order of 10 ppm.

Other Provisions

Evaporative Emissions. The Tier 3 regulation introduces new, more stringent evaporative emission standards. These include standards over 2-day and 3-day evaporative emission tests, which vary by vehicle categories and range from 0.300 to 0.500 g/test for light-duty vehicles and MDPVs, with 0.600 g/test for onroad gasoline-powered heavy-duty vehicles. The adopted evaporative emission standards also include a new "bleed test" and a new "leak test" requirements.

On-Board Diagnostics (OBD). EPA adopted and incorporated by reference current OBD regulations by the California ARB, effective for MY 2017, that cover all vehicles except those in the heavier fraction of the heavy-duty vehicle class.

Direct Ozone Reduction (DOR). Manufacturers continue to obtain an NMOG credit towards the combined NMOG+NOx standard for use of DOR technologies, such as radiators coated with ozone destruction catalysts. California methodology continues to be used for demonstrating the effectiveness of the technologies. The credit is limited to 5 mg/mi NMOG.

High Altitude Standards. Tier 3 standards introduce high altitude relief provisions to account for the lower air density and slower catalyst light-off at high altitudes. High altitude conditions are defined as those with a test altitude of 1,620 meters (5,315 feet) above sea level. (Under Tier 2, the same FTP emission bin standards applied to vehicles tested at both low and high-altitude.)

Manufacturers are allowed a limited relief for certification testing at high altitude. For sea-level certifications to Bins 20, 30, and 50, a manufacturer can comply with the next less-stringent bin for testing at high altitude. For example, a manufacturer can certify to Bin 50 for testing at high altitude versus Bin 30 at sea level. For vehicles certified at sea level to Bins 70 and 125, manufacturers can comply with standards 35 mg/mi higher (i.e., 105 mg/mi and 160 mg/mi, respectively). There is no high altitude relief for vehicles certified to Bin 160.

Enrichment Limitation for Spark-Ignition Engines. To prevent emissions from excessive enrichment in areas not fully encountered in the test cycles, the Tier 3 regulations impose limitations in the frequency and magnitude of enrichment episodes for spark-ignition light- and heavy-duty vehicles.

Phase-In Period Provisions. The Tier 3 standards include a number of provisions—such as alternative compliance options, flexibilities and requirements—applicable during the Tier 3 phase-in period. Some of these provisions include:

Relaxed In-Use Standards. Relaxed in-use NMOG+NOx standards—40% less stringent than the certification standards—apply to all vehicles certified to Bins 70 and cleaner as interim or final Tier 3 vehicles. The relaxed in-use standards apply during the entire percent phase-in period (i.e., through MY 2021).

Transitional Tier 3 Bins. Two transitional Tier 3 bins—Bin 110 and Bin 85, that have FTP NMOG+NOx standards of 110 mg/mi and 85 mg/mi, respectively (i.e., the sum of the NMOG and NOx values from the Tier 2 bins 3 and 4)—are available through MY 2019.

Interim 4,000 Mile SFTP Standards. Interim Tier 3 vehicles (i.e., vehicles which do not meet the final Tier 3 PM standards) must meet 4,000 mile SFTP standards, consistent with the existing Tier 2 and LEV II program requirements. This approach is designed to prevent excessive emission levels from individual vehicle models being masked by the averaging of the manufacturer’s fleet emissions.

ABT Program. Tier 3 regulations include an emission averaging, banking, and trading (ABT) program similar to those that have historically been a part of most EPA emission control programs.